The aim of this proposal is to understand the cellular and synaptic events that underlie changes in the songbird's capacity to learn new vocalizations. Adult male songbirds sing a song that is a copy of their tutor's song that they memorized as young birds. As juveniles, songbirds produce highly variable, imprecise copies of the memorized tutor song, which become more precise through a process requiring auditory feedback. Because the central circuit that controls song has been described, and the pace of song learning can be manipulated, the songbird provides an ideal experimental system in which to address the neural basis of this sensorimotor learning. Electrophysiological recordings will be made in brain slices prepared from zebra finches at two distinct developmental stages in order to characterize the synaptic connections onto neurons in a forebrain vocal premotor nucleus crucial for song production (RA), and to test the following hypotheses: 1) Modification of the synaptic connections between neurons in two forebrain regions involved in song production (HVc and RA) underlies vocal motor learning; and 2) Activity in an anterior forebrain regions (lMan), this is connected to RA, is necessary for this modification. A related hypothesis to be tested is that a loss of the capacity for synaptic modification between HVc and RA, due to a decrement in synaptic drive from lMan, underlies the loss of vocal plasticity that occurs with song crystallization.